1. Technical Field
This invention relates to a holding structure for a touch panel, which is provided at a display or an operation unit of a variety of electronic devices and being used as an input device.
2. Description of the Related Art
Conventionally, electronic devices having touch panel function as input means at the display surface have been widely used. One of the structures of the touch panels was a resistance-sensitive type. In the touch panel, a transparent ITO (indium oxide) film is formed on the surface of the touch panel glass in a predetermined pattern. Electrodes are connected to the end portion of the ITO film and the peripheries are coated by over-coating. And dot spacers are provided between the upper layer flexible substrate made of PET resin or the like and the lower layer glass substrate both on which ITO films are deposited. When an operator presses the surface of the touch panel, the ITO films on the upper and lower panels get in contact with each other. The pressed position on the panel is detected in accordance with the resistance value at that time.
The touch panel device is disposed overlapping on the liquid crystal panel or the like, and an operator carries out the input operation by directly touching such display surface. Even though the ITO films on the upper and the lower panels get in contact with each other when an operator presses the surface of the touch panel, the operator can neither feel nor be sure whether the contact is closed or not. And so, there is a touch panel with a so-called force feedback function which vibrates the touch panel by detecting the pressing operation and gives an operator an operation feeling.
As it is shown in FIG. 5, the touch panel device 1 equipped with the force feedback function is applied, for example, to handheld information equipment or the like. The liquid crystal panel 2 and the touch panel 4 are accommodated in the casing 6 made of resin or the like and the touch panel 4 is exposed from the opening 6a as it is shown in FIG. 6. The liquid crystal panel 2 is provided with a printed circuit substrate 7 and the substrate is held in a chassis 8. As it is described above, the touch panel 4 is composed of a flexible circuit substrate 4a provided at the front surface side and a glass substrate 4b provided at the rear surface side. The flexible circuit substrate 4a is a substrate made of PET resin or the like and a conductive pattern is formed on the front surface. The glass substrate 4b is a substrate made of glass and a conductive pattern is formed on the front surface. Moreover, piezoelectric devices for the force feedback purpose are disposed at the side edge of the touch panel 4.
In the case of the touch panel device 1 equipped with the force feedback function, elastic supporters 5 made of rubber or the like are provided at the four corners between the liquid crystal panel 2 and the touch panel 4 in the casing 6 in order to absorb the vibration of the touch panel 4 due to the piezoelectric device and to hold the touch panel 4. A bit of interspace 6b is formed between the peripheral edge of the opening 6a of the casing 6 and the front surface of the touch panel 4.
On the other hand, as a structure that secures the dust-proof feature and the drip-proof feature on the front surface of the touch panel for the touch panel with no force feedback function, there is a structure that the peripheral edges of the touch panel and the rear surface side of the opening of the casing of the touch panel device are bonded by way of a seal member, as it is disclosed in Japanese Patent Application Publication No. 2002-2229672. And, such a structure is proposed that a rubber packing holds the peripheral edge of the touch panel and both of the peripheral edge of the opening of the casing and a fixing member like chassis hold the rubber packing, as it is disclosed in Japanese Patent Application Publication No. 2000-276254.
In the case of the touch panel device equipped with the force feedback function shown in FIG. 6 of the related arts mentioned above, a bit of interspace 6b is disposed between the peripheral edge of the opening 6a of the casing and the front surface of the touch panel 4 in order to vibrate the touch panel, and there remains a problem that dust or drips are liable to enter from the outside and to give a bad influence on the liquid crystal panel 2 or other electronic elements.
On the other hand, as it is disclosed in Japanese Patent Application Publication No. 2002-229672 and No. 2000-276254, the dust-proof feature and the drip-proof feature become improved by making close contact and fixing the front surface of the touch panel with the peripheral edge of the opening of the casing, however, there remains a problem that the vibration of the touch panel is suppressed and the force feedback function comes to be deteriorated.